17 Million Year Old Sperm Found inside Shrimp Fossil in Australia

Scientists found the oldest preserved sperm in a shrimp dated more than 17 million years old.

In 1988, a group of Australian paleontologists came upon a fossil cave inside Australia’s vast Riversleigh World Heritage Fossil Site in northern Queensland. The cave had millions of bat fossils: bat bones, bat skulls, bat teeth and lots and lots of bat poop. That’s what the researchers thought they would get from the cave, bat fossils.

Turns out the limestone actually contained soft tissue of an ancient muscle shrimp known as an ostracod.

It was “absolutely extraordinary” that the animal’s soft-tissue had been so well preserved, said paleontologist Michael Archer, who co-authored a study published Wednesday in the Proceedings of the Royal Society B.

“The ostracods were living in a pool in a cave and for some bizarre reason the limestone has preserved the soft tissue,” said Professor Archer.

“The discovery of fossil sperm, complete with sperm nuclei, was totally unexpected. It now makes us wonder what other types of extraordinary preservation await discovery in these deposits,” Archer said in a statement.

“When you’re in the field picking up hard, dry rocks and smacking them with hammers the last thing you expect to find in those rocks is a piece of what was once living soft tissue.”

“These are the oldest fossilized sperm ever found in the geological record,” said Archer. “It’s staggering.”

The shrimp, measuring only about 1 millimeter long, but by proportion the bodily fluid inside it is enormous. If it were to be uncoiled, the shrimp sperm “can reach up to ten times the body length of its producer,” Science Daily reported.

The researchers found four female shrimp and one male.

The new study theorizes that mussel shrimp probably began deploying giant sperm for more than 140 million years.

“No one knows why ostracods have giant sperm or how they originated, and the new evidence that they have been around for millions of years only adds to the mystery,” micropaleontologist David Horne of Britain’s Queen Mary University of London told USA Today.

Research Associate John Neil, who works out of the Bendigo campus of the University said the perfectly preserved condition of the ancient shrimp has allowed scientists to compare the creature of the past with how it is today and very little has changed.

“This finding shows us that an organism as complex as the ostracod has changed very little in over 16 million years. Our ancient ostracod has almost an identical structure and organs to ostracods today. This find provides accurate information on the organism’s evolutionary status,” he said.